In internal combustion engines of certain configurations, for example engines with four in-line cylinders, excitations are created from engine out-of-balance forces and couples or moments generated by the rotating and reciprocating engine component masses. These excitations may be undesirable, particularly in mobile vehicles into which the engines may be fitted.
The transmission of engine excitations into a vehicle may be reduced by means of flexible engine mountings, although it is desirable in some vehicles, such as frameless tractors, to incorporate balance shafts driven by the engine to counteract such excitations.
Balance shafts are typically driven by a dedicated drive from a gear located at the front end of a crankshaft, and thus it is usual for the balance shaft assemblies to be installed within the sump of an engine, to be closely adjacent to the crankshaft. The balance shaft assembly will thus take up space that could beneficially be used for oil containment. A balance shaft assembly located in a sump may also cause aeration of the engine lubricating oil and may further be difficult to access for servicing.
Engines are typically provided with front end accessories in the form of alternators, fans, power steering pumps, air conditioning pumps and the like. A front end accessory drive is typically provided by a pulley in communication with the engine crankshaft nose (i.e. externally of the engine). However, direct communication between the pulley and the crankshaft nose results in significant engine noise. More particularly the pulley, being typically disc or bell-like in construction, acts like a loud speaker to transmit engine noise from the engine.
Further, the crankshaft pulley is generally located at an end of the engine that is frequently relatively exposed to the radiator air intake opening of the vehicle, thus the engine noise emitted via a crankshaft pulley may add significantly to the vehicle's ‘drive-by’ noise.
Moreover, a seal must be provided at the front end of the engine at the crankshaft to prevent oil leakage and dirt ingress. However, such a seal is vulnerable to damage due to shaft rotation and dirt contamination.
The present invention sets out to overcome these and other disadvantages of the prior art.